1. Field of the Invention
The invention relates to a method for visualizing a particular surface of an object volume in an overall medical/biological environment, through establishing at least a first and a second contour surface within the above environment that collectively define a target object volume and which method allows to selectively exclude information pertaining to structures outside said target object volume.
2. Related Art
Medical/biological MR (magnetic resonance) diagnostics, medical/biological CT (computer tomography) and US (ultrasonic) technologies have all recognized the importance of visualizing only limited target object volumes while excluding volumes out-of-interest. A relevant but non-limiting example is the visualizing of coronary arteries by excluding information outside the heart's wall that could obscure these objects of interest (e.g., in this case both the interior ventricles of the human heart and also structures that lie outside the immediate neighborhood of the heart). In this example, when visualizing a beating heart, the contour data that identify the volume-of-interest will be depending on the phase of the heart's beat cycle. Therefore, synchronizing to an ECG (electrocardiogram) will be required for visualizing successive slices that belong to respectively selected phases in the cycle. By themselves, methods for executing such synchronizing are widely known in the medical profession.
U.S. Pat. No. 6,058,218 to Cline discloses the applying of a threshold level to the data, smoothing the thresholded data set, dilating the smoothed data set, excluding certain data from the original data set as based on the smoothing result, and imaging the non-excluded data. Cline's masking/dilating operations substantially reduce voxels intensities to a binary value. Subsequently, the dilating is effected by subjecting the voxel environment to uniform binary operators. Now, the reference has recognized that often, starting from the inner contour of the heart will yield better results. Effectively, the prior art creates a watermark-surface, and thereafter effects the visualizing as being based substantially on voxels on both sides of the watermark. Through binarizing the image and using relatively simple operators, the versatility of the reference is limited, as will be discussed further hereinafter.
Indeed, the present inventors have recognized that the above procedure will in many instances render less accurate results where the various surfaces (inner versus outer) are to a certain degree running independently from each other. In the example of a human heart, the wall thickness may vary over an appreciable factor, and the uniform dilating process as discussed supra would thus be liable to underestimating the wall thickness in thicker places, and overestimate the thickness in thinner places.